Oxidation
Oxidation
Oxidation is a chemical reaction that occurs when oxygen in the air comes in contact with the alcohol in wine, converting ethanol into acetaldehyde, then acetic acid. It causes wines to lose their vibrant colors: white wines become brown, red wines develop orange hues. It also reduces fresh fruit aromas and introduces nutty or vinegar notes. Although it is harmful in excess, controlled oxidation is beneficial while aging wine.
See Also
Yeast
Yeast in wine is a microscopic, single celled fungus, typically Saccharomyces cerevisiae, which triggers fermentation by transforming the sugars in must into ethanol and carbon dioxide. Yeasts are essential for converting grape juice into wine and they determine its final alcohol content, aroma and flavor profile.
Dosage
Dosage is the final step in producing traditional sparkling wine (such as Champagne) where a small amount of wine and sugar, known as liqueur d'expédition is added to the wine after sediment is removed (disgorgement), just before corking.
Viticulture
Viticulture is the branch of science that deals with the study, cultivation and harvesting of grapes specifically for winemaking. It includes all vineyard activities, such as planting, pruning, training vines, soil irrigation and pest control.
Anthocyanins
Anthocyanins are natural polyphenol pigments located in the red grape skins, responsible for the red, purple and blue colors in young red wines. They determine the wine's hue, shifting from vibrant red to brownish orange as they age.
Must
Grape must is the freshly pressed, unfermented grape juice which contains the fruit's skins, seeds and sometimes stems (collectively referred to as pomace).
Sulfites
Sulfites (sulfur dioxide or SO₂) are chemical compounds naturally produced by yeast during wine fermentation. They act as preservatives, also commonly added by winemakers to prevent bacterial growth, spoilage and oxidation.
Irrigation
Irrigation is the artificial application of water to vineyards to provide the necessary 25-35 inches of annual water in dry climates.
pH
The pH of wine is the measure of its total acidity (hydrogen ion concentration), typically ranging from 2.9 to 4.0 in most wines.